Understanding MIMO Systems: Multiple Input Multiple Output Wireless Communication, Study Guides, Projects, Research of Mobile Communication Systems

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Multiple Input Multiple Output

Wireless Systems

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Presentation Outline

 Introduction

 What are MIMO Systems???

 How MIMO Functions???

 Categories of MIMO systems

 Spatial Multiplexing  Spatial Diversity  Smart Antennas

 Applications

 Drawbacks

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What are MIMO Systems???

 MIMO is acronym for Multiple Input Multiple Output systems.  The basic idea behind these systems is to use multiple antennas at transmitter and receiver to improve communication performance.  Why we can not achieve high data rates and small error rates with existing SISO technology?  Spectrum available is limited  Transmit power is limited  Why MIMO is better than existing SISO technology??? MIMO is resistant towards multipath propagation and fading effects

 Multipath propagation seriously degrades the performance of

SISO systems.

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Wireless Systems

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Categories of MIMO Systems

 MIMO systems are characterized into three categories on the

basis of their benefits:

 Higher Bit Rates with Spatial Multiplexing  Smaller Error Rates through Spatial Diversity  Higher Bit Rates and Smaller Error Rates through Smart Antennas

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Spatial Multiplexing

 Spatial multiplexing techniques promise to give high bit rates

without requiring extra bandwidth or extra transmission

power.

 Scheme

 At the transmitter, the information bit sequence is split into M sub-sequences.  Sub-sequences are modulated and transmitted simultaneously over the transmit antennas using the same frequency band.  These are combined at receiver.

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Spatial Multiplexing

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Spatial Diversity

 The spatial diversity techniques aim to provide improved

error performance by increasing the Signal to Noise Ratio

(SNR).

 Scheme

 Firstly the data is coded using space-time coding.  Then the multiple copies of the data are transmitted through the multiple antennas.  The redundant signals are then combined at the receiver using some detection algorithm.

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Spatial Diversity

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Smart Antennas

 In addition to higher bit rates and smaller error rates, they also improve the signal-to-noise ratio (SNR) and suppress co-channel interference at the receiver.  The smart antennas use Beamforming techniques.  Beamforming is a signal processing technique in which signals are superimposed constructively and destructively, as desired, to control the direction of transmission and reception of signals.  The smart antennas apply beamforming to steer signals in desired direction and suppress them in undesired direction, thus leading to improved SNR.  Antenna Gain or Array Gain

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Applications

 Because of the high bit rates and reduced errors, MIMO

systems have become an important part of modern wireless

communication standards such as

 WiFi IEEE 802.11n  4G – Fourth Generation Mobile Communication Networks  WiMAX  Mesh Networks – Special type of Ad-hoc Networks  Radio Frequency Identification (RFID)

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Drawbacks

 MIMO systems offer various benefits in wireless

communication but they also have certain disadvantages

 Hardware costs are increased due to multiple chains of transmitter and receiver antennas.  Power consumption requirements for hardware equipment are increased.  The signal processing involved increases the complexity of the system.  Real-time implementations of near-optimum MIMO systems can be challenging.

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Thank You

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